1. Field of the Invention
The present invention relates to a method for the preparation of organic chelates and, more particularly, to a method for the preparation of organic chelate minerals with a high absorption rate having the organic chelates used as ingredients for animal feedstuffs that are not easily decomposed in a stomach and delivered to the intestines.
2. Description of the Related Art
Properly assorted animal feedstuffs containing various kinds of nutrients have been developed and used to improve productivity of livestock which is a major source of proteins for humans. Specific amounts of iron, copper, zinc, and potassium are essential for the normal growth of the livestock. Even though the contents of minerals are very low in an animal, they have various functions such as forming skeleton, adjusting an osmotic pressure within a body, maintaining an acid-base balance of the body fluids, and acting as an activator in an enzymatic system or a constituent of enzyme itself. These minerals are supplied to the livestock from external sources since they are not synthesized in the body. Therefore, these minerals should be contained in the animal feedstuff to feed the livestock. Inorganic minerals according to the prior art have the salt forms of chlorides, sulfates, nitrates, phosphates, and carbonates. However, the absorption rate of inorganic minerals in a living body is so low that excessive amounts of minerals are fed to the livestock. Unabsorbed minerals are excreted as feces, which are then recycled to the soil. Through this process, the accumulated minerals, which give fatal damages to the ecosystem of the soil, increase the soil contamination.
An introduction of organic chelates has been suggested to solve the problems cited hereinbefore since organic chelates may highly be absorbed in a living body. Because of a high absorption rate of organic chelates in a living body, a relatively small amount of organic chelates included in the animal feedstuff fulfills the metabolic requirement of minerals and reduces the soil contamination. In the late 1980's, it was reported that organic chelates prepared from the reaction of metal compounds and carbohydrates or proteins have a high absorption rate of 70˜80% in comparison with that of the inorganic minerals (Kratzerand Vohr. 1986).
The term of chelate is not a new concept. It is adopted from the structure of a divalent iron or a magnesium ion located respectively in the center of hemoglobin or chlorophyll and surrounded by organic amino acids or porphyrins. The chelates, hemoglobin and chlorophyll are essential compounds in maintaining the life of living things.
For examples, Korean Patent Publication (hereinafter referred to KP) number 1991-5777, 2000-53858, 2002-6112, 2002-6113, and 2002-6114 are disclosed to provide organic minerals. KP No. 1991-5777 relates to a method for preparation and utilization of easily absorbable iron proteinate into the body and discloses a method for the preparation of iron proteinate by chelating divalent iron ion with oligopeptide obtained from the hydrolysis of proteins. KP Nos. 2002-6112, 2002-6113 and 2002-6114 relate respectively to a method for the preparation of easily absorbable copper proteinate into the body, a method for the preparation of sodium proteinate that is not ionized in the vein after absorption in the body, and a method for the preparation of easily absorbable zinc proteinate into the body. These inventions disclose the methods for preparation of chelate compounds having metal ion oligopeptide by the following procedure. Oligopeptides are produced by adding 2˜4 weight % protease and reacting the proteins suspended in purified water at pH 3.5 to 6.0 for 11 to 12 hrs. A chelate reaction between a mineral ion such as copper, sodium, or zinc and the above oligopeptides is occurred so that a metal ion oligopeptide chelate is formed. The above prior arts have disadvantages that the procedures are complicated and require high preparation cost since minerals are bonded to the proteolytic products. KP No. 2000-53858 relates to a preparation method of metal chelates and utilization in animal feedstuff, and discloses a preparation method of organic chelates as follows. Metal oxide, metal powder, metal carbonate, or metal hydroxide is added to amino acid or the hydrolyzed product of animal/vegetable proteins in water at the pH 5.5–8.5, and then the mixture is heated up in the range from 60° C. to boiling point of the solution in inert atmosphere. However, metal powder, metal oxide, metal carbonate, and metal hydroxide are sparingly soluble in water, and the above metal ions are not completely ionized in the solution. The disclosed inventions have a disadvantage that in the above pH range, only ionic bond is formed and coordination bond is not formed, so that the chelate formation between metal ion and amino acid is not accomplished. This method does not show any specific effect compared to the method using inorganic minerals in animal feedstuff.
Additionally, KP 2003-6877 relates to a manufacturing method of animal feedstuff additives containing methionine-iron chelates. According to this method, the ratio of methionine and iron is 1:1 or 1:2 and the dissolving temperature of methionine should be below 70° C. The methionine, however, is not completely soluble in the suggested temperature and the above method describes simply that an alkali solution is utilized. If a high reactive material such as potassium or sodium hydroxide is used in the alkali solution and the reaction of FeSO4+NaOH→Fe(OH)2+Na2SO4 progresses completely, then a chelate compound may be formed. However, the solubility of methionine is dramatically increased due to the formation of the salt form, —COO−M+, between —COO— of methionine and M+ (sodium or potassium) of alkali, and thereby the dissociation between methionine and metal ion is caused. Accordingly, the bonding between methionine and divalent iron ions may partially be formed, however inorganic salts such as iron hydroxide and iron sulfate may also be formed at the same time.
A chelate mineral as a single amino acid mineral chelate having a high absorption rate and buffering capability is not yet disclosed up to now internationally. Chelate products according to the prior art do not have a concrete coordination bonds and features as a single amino acid chelate. In this regard, the organic chelates having a high absorption rate are not yet developed so far. Commercially available single amino acid chelates are produced by an evaporation, condensation and drying processes, indicating that concrete bonding is not yet induced.